Cleaning shoes are major subsections of agricultural harvesters. Cleaning shoes are generally constructed as a housing that encloses a fan and one or more reciprocating sieve assemblies. The fan generates a flow of air that passes upward through the sieve assembly as the sieve assembly reciprocates fore and aft. This airflow lifts material other than grain (MOG) such as chaff or dust and carries it rearward out of the agricultural harvester where it is deposited on the ground. The grain is dense enough that it resists this flow of air and is not carried rearward, but instead falls downward through the sieve assembly onto a pan that extends underneath the sieve assembly. A transverse conveyor in the pan carries the grain to one side of the agricultural harvester, and a vertical conveyor carries the grain upward and into a grain tank or reservoir located at the top of the agricultural harvester.
To assist the air in separating the grain from the MOG, the sieve assembly is reciprocated in a generally horizontal plane. The speed of reciprocation is on the order of 300 cycles per minute. A typical reciprocating sieve assembly comprises a generally rectangular frame that supports one or more sieves.
The sieves are generally formed as dozens of these slats, each of which extends side to side with respect to the agricultural harvester. These slats are supported, in turn, in a second frame that is supported inside the generally rectangular frame.
The reciprocating sieve assembly is typically supported on hangers that extend generally vertically. The upper ends of the hangers are fixed to the chassis of the agricultural harvester. The lower ends of the hangers are fixed to the reciprocating sieve assembly. A power source, such as a motor with a rotating shaft, is connected to the hangers with an offset crank and rod arrangement. As the motor rotates, the hangers are pivoted fore-and-aft at their lower ends by the rod to shake the reciprocating sieve assemblies. This reciprocation jostles the dirty grain falling on the sieve, spreads the grain out more evenly across the surface of the sieve and enhances the flow of air through the dirty grain.
Cleaning shoe design, and particularly the design of the reciprocating sieve assemblies, is a trade-off between strength, durability and weight. The cyclical loading of the reciprocating sieve assemblies tends to cause fasteners to loosen. For this reason, the reciprocating sieve assemblies are typically welded together. Unfortunately, the welds are also prone to failure by metal fatigue due to the reciprocating loads placed on the individual members which is compounded by inhomogeneities and other flaws in the welds.
What is needed, therefore, is a new configuration for a reciprocating sieve assembly that weighs less and is more immune to the cyclical stresses.
It is an object of this invention to provide such an arrangement.